Insulation for meter troughs



Feb. 14, 1939. G E PALMER 2,146,843

INSULATIGN FOR METER TROUGHS Filed April 9, 1938 ,JZw/ZZW fwwifdwPatented Feb. 14, 1939 UNITED STATES PATENT OFFICE 4 Claims.

This invention relates to troughs or boxes on which electric meters areadapted to be removably mounted.

Troughs of this kind have come into wide use and are illustrated anddescribed, for example, in the McKinley and Palmer application SerialNo. 156,760, filed July 31, 1937; in the Bradshaw and Johanssonapplication Serial No. 118,590, filed December 31, 1936, and in thePalmer application Serial No. 186,791, filed January 25, 1938. Thesetroughs are characterized by covers having circular openings of aboutthe same diameter as a meter, each opening being surrounded by anoutturned flange. A ring is mounted on the cover around such opening toform a base to which a meter may be secured. Within the trough or boxand accessible through such circular opening are connection means andclips by which a number of blades projecting rearwardly from a meter maybe electrically connected to circuit wires or bussing members in thetrough when the meter is mounted in place over the opening. Theseconnection means include devices having contact elements which can beoperated by means of a screwdriver or other equivalent tool through theopening to connect and disconnect the clips from their correspondingcircuit wires or bussing members. In troughs of this type which are nowon the market, such devices are located in the trough nearly in linewith the edge of the circular aperture, so that it is diflicult tooperate these devices without the tool touching the flange whichsurrounds the aperture or the ring which surrounds the flange. Sincesome of these contact devices are usually charged and the trough isalways grounded, contact of a metal screwdriver with both will result ina short-circuit. While screwdrivers covered with insulation are oftenused, such insulation is subject to wear and is therefore unreliable asa protection against such short-circuits.

According to the present invention, insulation is mounted on the troughcover itself and is also arranged so as to be out of the way but to beeffective in preventing contact between a screwdriver and any metal partof the trough, including its cover and the ring thereon.

For a more complete understanding of the invention, reference may be hadto the following description of an embodiment thereof, and to thedrawing of which Figure 1 is a fragmentary elevation of a covered troughinsulated according to the invention.

Figure 2 is a perspective view of an insulating member to be applied toa ring and cover of a meter trough.

Figure 3 is a fragmentary perspective view of a ring and a portion of atrough cover on which the ring is mounted.

Figure 4 is a fragmentary perspective view of the ring and insulatingmembers assembled together.

Figure 5 is a section on the line 5-5 of Figure 4.

Figure 6 is a section on the line 6-6 of Figure 4.

Figure 7 is an end elevation of a trough and meter.

Figure 8 is a fragmentary elevational view of a slightly modified formof the invention.

Figure 1 shows a trough or box Ill having a cover I2. Since such troughsare usually mounted with their bottoms against vertical supportingsurfaces, the cover l2 may be described as the front wall of the trough.The cover or front wall 12 may be composed of one or more sections orpanels, each having one or more large circular openings therein. Onesuch opening is shown in Figure 1, this opening being surrounded by anout-turned flange l3 and a ring M. The latter may be permanently securedto the front wall l2 or may be removably attached thereto. This ringreceives and supports a meter l5 (Figure '7). In the structureillustrated in Figure l, the ring [4 is provided with a diametral crossbar I6 integrally cast therewith to support a pair of insulating blocksl8 and 20 which are attached thereto as by screws 22 and 24, and aseries of inner lugs 25, 25a to center the meter. The ring [4, and withit the corresponding section of the front wall I2, may be anchored tothe trough by a pair of screws 26 and 28 which pass through the crossbar l5 and screw into the rear wall of the trough l0. When the meter isin place on the ring l4, these anchoring screws are inaccessible. Ablock of insulation 30 is secured against the rear wall of the trough asby screws 32 and 34 and is provided with suitable connectors orterminals 36, 38, and 42 which are adapted to clamp onto strippedportions of circuit wires or bussing members within the trough. Mountedon the blocks l8 and 20 are clips 44, 46, 48 and 50 which are adapted toreceive connecting blades 5| projecting rearwardly from the meter l5.These clips are normally connected to respective terminals by switchingmeans 52, 54, 56 and 58 respectively. Such switching means are describedand illustrated in details in the McKinley and Palmer applicationhereinbefore referred to, and may include screws or other rotatableelements which are accessible by a tool projecting through the opening.As shown, the switching devices 52, 54, 56 and 58 are nearly in linewith the edge of the opening so that a tool or screwdriver inserted toengage any one of these switching devices will be very close to theflange l3 and ring l4 and will be apt to come in contact therewith.According to the present invention, those portions of the flange l3 andring M are provided with suitable insulating shields to avoidshort-circuits. As indicated in Figure 3, the ring 14 surrounds theflange l3 and is secured to the outer face of the front wall l2, theinner diameter of the ring I being slightly larger than the outerdiameter of the flange so that an annular clearance or slot 62 is leftbetween the ring and the flange. Flexible strips 66 of insulatingmaterial, shaped as indicated in Figure 2, are mounted within the ringI4. The strips 66 are sufficiently thin to enter the clearance 62between the flange l3 and the ring l4, and are preferably of suchresilient shape-retaining material that, when bent to the arcuate shaperequired to fltinto the ring M, the strips tend to spring back intoplane shape. Bakelite or an equivalent plastic is suitable for thispurpose. The inner edge of each strip is cut so that portions 68 extendbeyond the adjacent portions 69 of the strip and are separated therefromby slots ill. The outer margin of the strip is cut away at the endsthereof as at 12, this resulting in end tongues M which are narrowerthan the body of the strip. The strip is mounted within the ring M insuch a manner that the portions 68 project through the opening and bearagainst the inner face of the flange l3, thus covering inner faceportions of the flange and ring as indicated in Figure l, the remainingportions GS-of the strip being inserted in the clearance or slot 62between the flange and the ring. The width of the strip is such that,when the strip is thus seated, its outer edge is substantially flushwith the outer surface of the ring Hi. If the strip is inserted in thering before leaving the factory where the trough covers are made orassembled, it is desirable that it be firmly secured in place to preventloss during shipment or in handling prior to installation. To this end,the strip may be made of sufiicient length so that the ends of thetongues M project beneath the ends of the cross bar it where the crossbar joins the ring. This serves to hold the ends of the strip in theslot 62.

The middle of the strip may be anchored in any suitable manner. Anadhesive may be used in the slot 62, or, as shown, the flange l3 may beindented as at 76 by a punch or other suitable tool so that the strip isfirmly pinched at that point between the flange and the ring, Thus thestrip is anchored at both ends and the middle and is firmly secured inplace. The portions 68 cover the portions of the flange it which areadjacent to the switching devices 52, 54, 56 and 58, so that the flangeand ring, including the lugs 25, a, are permanently and effectivelyinsulated from accidental contact of a screwdriver or other tool usedfor the operation of the switching device.

For insulating rings or troughs which have already been installed andare in use, it is sufiicient to anchor the ends of each strip and todepend on the resilience or springiness of the strip to hold it inplace.

Meter-supporting rings of the kind illustrated are customarily made witheight inner lugs. 01' these the four which are nearest to the cross barIt are designated by the reference character 25; the others by thecharacter 25a. In the meter-connection mechanism shown in Figure 1 ofthe drawing, the switching devices are shown as near to the lugs 25. Inlarge numbers of troughs now in use, the switching devices aredifferently mounted on the blocks l8 and 28 so that they are near thelugs 25a. In such cases it is not necessary for the strips to cover thelugs 25 and shorter strips may be used, the end tongues of these stripsbeing caught under the lugs 25 to anchor the strips, as shown in Figure8.

Instead of two semi-circular insulating strips 66, four shorter elementsmay be employed, one

for each of the switching devices, or a single strip approximately equalin length to the circumference of the flange l3 may be employed. Such asingle strip would have to be assembled with the ring and front wallbefore the ring is secured in place.

It is evident that various modifications and changes may be made in theembodiments of the invention herein shown and described withoutdeparting from the spirit or scope thereof as defined'in the followingclaims.

I claim:

1. Apparatus of the class described, comprising a box or trough having afront wall with a large circular opening therein and an out-turnedflange surrounding said opening, a meter-receiving ring secured to saidfront wall and surrounding said flange with a slight annular clearancebetween, a connection device mounted within said box in a position to beoperable by a tool inserted through said opening adjacent to an edgethereof, and an insulating shield secured within said ring andflange'adjacent to said connection device, said shield comprising aflexible strip of insulation material having a marginal portionprojecting into said opening against the inner face of said flange andother marginal portions disposed within said clearance.

2. Apparatus of. the class described, comprising a box or trough havinga front wall with a large circular opening therein, the margin of saidwall about said opening being out-turned to form a flange, a ringsurrounding said flange and mounted on said wall to receive a meter, thering and fiange'having a narrow annular clearance between them, adiametral cross bar integral with said ring and extending across saidopening, and a pair of strips of insulating material mounted within saidring, each said strip having its end portions disposed in said clearanceand engaged under said cross bar, each said strip having a mid-portionextending into and secured in said clearance and intermediate portionsextending from the rim of said ring through said opening so as to coverthe adjacent inner face portions of the ring and flange.

3. Apparatus of the class described, comprising a box or trough having afront wall with a large circular opening therein, the margin of saidwall about said opening being out-turned to form a flange, a ringsurrounding said flange and mounted on said Wall to receive a meter, thering and flange having a narrow annular clearance between them, and athin strip of insulating material shielding a portion of said ring andflange, said i strip having a marginal portion engaging the inner faceof said flange and another marginal portionpinched between said flangeand ring to hold the strip in position.

4. Apparatusof the class described, comprising a box or trough having afront wall with a large circular opening therein, a margin of said wallabout said opening being out-turned to form a flange, a ring surroundingsaid flange and mounted on said wall to receive a meter, a narrowannular clearance between the said ring and the said flange, lugs on theinner face of said ring, and a thin strip of insulating materialshielding certain of the said lugs and a portion of said ring and saidflange, the said strip having a marginal portion engaging the innerfaceof said flange and extreme portions of said strip lying beneathcertainof the said lugs and also between the said ring and said flangeto hold the strip in position GRANVILLE E. PALMER.

